1. Field of the Invention
This invention relates to telecommunications services and more particularly to a method and system for facilitating transmission of analog signals to a wireless terminal.
2. Description of Related Art
A wireless terminal is a form of telecommunication technology that enables people to communicate with others. The wireless terminal can take a variety of forms. The wireless terminal may be, for example, a cellular phone, a pager, a personal digital assistant (PDA), a portable computer with wireless modem, or a fixed wireless terminal.
The wireless terminal exchanges signals with a radio access network. The radio access network communicatively couples the wireless terminal to a remote terminal. The remote terminal may be, for example, another cellular telephone, a pager, a PDA, a portable computer with wireless modem, or a fixed wireless terminal.
The radio access network typically has a base transceiver station (BTS) and a base station controller (BSC) (collectively referred to as a “base station”). The wireless terminal exchanges signals with the BTS and the BSC. The radio access network may also have a mobile switching center (MSC), an interworking function (IWF), and an IP network. The BSC may be coupled to the MSC, which is in turn coupled to the IWF and IP network. Additionally, the radio access network may have a BSC coupled to a packet data serving node (PDSN) and the IP network. Therefore, the radio access network facilitates wireless communication with the IP network.
The base station has a basic architecture that consists of radio-frequency (RF) power amplifier, a radio frequency section, a sampling and reconstruction system, and a signal processing system. The RF power amplifier, radio frequency section, sampling and reconstruction system, and signal processing system collectively facilitate exchange of signals with the wireless terminal.
In a transmit mode, the base station receives a digital signal from the MSC or the PDSN and transmits an analog signal to the wireless terminal. The digital signal may be defined by a plurality of channels. The signal processing system amplifies each channel of the digital signal to a power level. Then, the digital signal is passed to the sampling and reconstruction system. The sampling and reconstruction system has a digital-to-analog converter (DAC) that converts the digital signal from the MSC or the PDSN into the analog signal. A plurality of channels, typically 128 channels in a carrier division multiple access (CDMA) protocol, may define the analog signal. The radio frequency section modulates the analog signal at a modulation frequency. Finally, the RF power amplifier adds a fixed gain to the analog signal and outputs the analog signal to an antenna for transmission to the wireless terminal.
In a receive mode, the base station receives an analog signal from the wireless terminal and outputs a digital signal to the MSC or to the PDSN. The RF power amplifier receives the analog signal at the antenna. The RF power amplifier adds a fixed gain to the analog signal and the radio frequency section demodulates the analog signal to a base band signal. The sampling and reconstruction system has an analog-to-digital converter (ADC). The ADC converts the base band signal into a digital signal and outputs the digital signal to the MSC or to the PDSN.
This basic architecture allows for the base station to transmit and receive signals with the wireless terminal.